Download - LS Dyna Tutorial FEA

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Page 1: LS Dyna Tutorial FEA

Example Plate impacting Plate

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Definition A Shell Elements drop and rebounds from a elastic plate. Plate measure 40*40*1 mm3 (16 elements) Dropped shell has 10mm side length and 2 mm thickness. Drop height is 10mm Element formulation is Belutschko-Tsay Define a surface to surface contact with 2 way detection. Define the elastic plate as Master and impacting shell as slave. Initial Velocity is 100,000 mm/sec vertically End Time is 0.0002 sec.

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Set-Up For model setup we use various option in the preprocessor tab. Create 2 areas with required dimension as shown below (Preprocessor-Modeling-create-). Transform drop shell to required drop height.

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Meshing

Part Material Element Type Real constant

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2 1 1 2

Define Element Type 163 (Preprocessor-Element type-add/edit/delete-)

Part should be defined using right combination of material , real contact , element type. Before meshing this has set and can be confirmed at status bar.

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Meshing cont…Define Real Constant to assign section properties

or thicknesses. For each thickness there should be one real constant. (Preprocessor-Real Constants)

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Meshing Cont…Material PropertiesDefine material properties for various parts using option

shown below. (Preprocessor-Material Props-Material Models)

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Creating Parts Assign the correct material, section properties and element type

to create parts. For LS-Dyna to recognize a part, its should be a group of elements

that have the same combination of element type, real constant set, and material reference numbers

Repeat this to all area/components (Preprocessor-Meshing – Mesh Attributes)

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Revisiting MeshingSet line seeding or element size. (Preprocessor-Meshing-Mesh tool-Set)Mesh Volume ,Areas and lines to generate solid, shell or beam

elements.Refer images below to access the meshing tool.

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Creating ComponentsWe need to create node and elements components for

Adding Constrains to a group of nodesDefining Velocity to a part (part nodes need to be grouped)Defining a master surface and node surface (associated nodes of

surface need to be grouped)To request output for required parts/region of interest.In this model create node and element component for both the

areas you could name them for example as plate_e and plate_n for element and node components. Refer images below to access the menu options.

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Adding Constrains to Model The plate is fixed at its boundaries (Preprocessor-LS-DYNA-Constraints-On Nodes) Create a node component or select the desired nodes to apply the constrains. Refer images below to access the menu options to add constrain.

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Defining contacts In this model we will create a Automatic Surface to Surface Contact.

Choose the moving plate as contact surface and fixed plate as target surface. (Preprocessor-LS-DYNA-Contact-DefineContact)

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Initial Velocity The moving plate has initial velocity of 100,000 mm/s in vertical

direction. Initial velocity can be applied using option under LS-Dyna Option tab

as show below. (Preprocessor-LS-DYNA-Initial Velocity-w/Nodal Rotate)

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Solution SettingAs per problem definition end time is 0.0002 sec, remember

that most of impact problem occur over a time of ms.We now use option in the solution tab (Solution – Time

Controls – Solution Time)

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Output Controls In output controls we

Request for both Ansys and LS-Dyna Result formats Set the frequency at which result files are written Request for Special Ascii files which has information on system energies, Nodal and Elemental

results. Select the components for which Time-History results has to be written.

You could request for 10 Ascii files at a time the most frequent used are Global statistics dataBoundary condition forces and energyMaterial energies summaryGeometry contact entitiesNode data

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Solution and ResultsClick on the Solve option in run the simulation (Solution – Solve)

As Discussed before this example Post processing option are General Post Proc Time History Post Pro Attached is the animation of the solved problem.

Utility Menu > PlotCtrls > Animate > Over Results

test.avi

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Time- History Post ProcessingTimeHist Postpro > Variable Viewer > File

> Open > Explicit Dynamics Results (*.his) > Jobname.his

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